July 18 (Reuters) - Iran's Supreme Leader Mojtaba Khamenei said in a written statement on Saturday that repeated U.S. breaches of a memorandum of understanding signed by the presidents of Iran and the United States had shown that President Donald Trump's signature was "utterly worthless and devoid of credibility."

Washington and Tehran have exchanged strikes after a ceasefire agreement fell apart last week, raising fears of a return to all-out war.

FRANKFURT, July 18 (Reuters) - Germany is upgrading its security stance to a "high threat level" from a previous"abstract threat level" based on increasing reports and intelligence, the country's Interior Minister Alexander Dobrindt said in a German newspaper interview published on Saturday.

• "This means that the risk of attacks must be reckoned with at all times in Germany," he was quoted as telling Welt am Sonntag.

• “Plans for attacks against our country are clearly discernible,” he added.

• He cited risks to German infrastructure, individuals and institutions.

By Matt Spetalnick

WASHINGTON, July 16 (Reuters) - President Donald Trump has ramped up U.S. air strikes on Iran and threatened broader escalation, but there is little sign that a military strategy that has already failed to extract concessions from Tehran will succeed this time.

With the collapse of an interim ceasefire deal reached a month ago, Trump finds himself in a bind as he seeks to break Iran’s grip on the vital Strait of Hormuz and force Tehran to accept his demands.

By Manuel Silvestri

VENICE, July 17 (Reuters) - A few hundred people in Venice protested on Friday against U.S. Ambassador to Italy Tilman Fertitta as he arrived in the lagoon city aboard his superyacht, drawing criticism of President Donald Trump's policies.

Activists also objected to the heightened security measures put in place by local authorities as Venice prepares for one of its most important festivals.

By Kanishka Singh and Jasper Ward

WASHINGTON, July 17 (Reuters) - The U.S. military said late on Thursday it completed its latest wave of strikes on Iran that were carried out at President Donald Trump's direction and marked a seventh consecutive night of American attacks.

Here are details:

• "U.S. forces employed fighter aircraft, aerial drones, and warships in addition to other assets," the U.S. Central Command said in a statement.

By Jana Choukeir, Enas Alashray, Ahmed Tolba and Menna AlaaElDin

DUBAI/CAIRO, July 17 (Reuters) - The United States on Friday launched a seventh straight night of attacks on Iran, which in turn struck U.S. allies in the Gulf, as both sides targeted infrastructure while shipping in the Strait of Hormuz came under further assault.

By Catherine Cartier and Jonathan Saul

July 17 (Reuters) - A vessel under sanctions for moving Russian fuel is likely leaking oil in a protected marine area off the coast of Oman, according to analysis of satellite imagery and experts.

The Caroline Bezengi vessel took Russian oil on board in Novorossiysk before leaving for its most recent voyage, according to ship tracking data. It last transmitted a signal on public AIS tracking on June 11 off the coast of Yemen.